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High-flow air valves simplify router design

DN Staff

November 29, 2004

4 Min Read
High-flow air valves simplify router design

Precision PCB Products used the VM10 valves to simplify the design and reduces costs on its new Final Touch 101 printed circuit board router.

Using a compact, high-flow pneumatic valve manifold, engineers have simplified the design of a new printed circuit board routing machine. The machine, designed by engineers at Precision PCB Products (San Clemente, CA), used pneumatics instead of electric motors as a means of holding printed circuit boards in place during the so-called "de-panelization" process, in which small circuit boards are cut from large electronic panels. By doing so, engineers said the OEM was able to deliver a smaller, tidier machine.

"We were able to put all the pneumatics in a very small package," notes Mike Gibbons, district sales manager for Norgren, Inc. (Los Angeles, CA), which supplied the pneumatic components. "The valve stack that we used weighs only four or five pounds." Gibbons adds that the six-valve stack measures a mere 5.25 inches long, making it more than 20 percent shorter than a comparable stack using a more traditional design.

In the routing application, OEM engineers employed the compact valve stack as a means of controlling and delivering pressurized air to tiny air cylinders that hold the printed circuit boards in place during the routing process. They say that the ability to eliminate inches in applications such as those, as well as in other tightly packaged applications, such as end-of-arm robotics and pick-and-place machinery, is critical.

The company claims that the key to the creation of the smaller, lighter stack is twofold: Norgren engineers incorporated small, high-flow valves; and they employed a unique manifold design that combines the so-called "sub-base" with the valves in a single block.

"Traditionally, you'd have a pneumatic sub-base and an electrical sub-base, and you'd screw the valves on top," says Brady Webb, valves business development manager for Norgren, Inc. (Elk Grove Village, IL). "But by combining the sub-base and the valve into a single block, we cleaned up the flow path and maximized air flow through the valve." Indeed, Norgren's 10-mm-wide VM10 valves used in the application offer a Cv of 0.440 (440 liters/min), approximately two to three times more than that of competing pneumatic valves of similar size.

Norgren engineers attribute the higher flow capabilities to a hinged design that connects the sub-base to the valves. The hinge, they say, eliminates the need for tie rods, which reportedly take up space and contort the flow path, which in turn lowers the flow rate. In contrast, Norgren engineers say that by eliminating the tie rods, they've cleaned up the valve's internal configuration.

"The internal pathways that go to the pressure ports and outlet ports on this valve are very wide open," Gibbons says. "It's a direct shot through the valve, so you don't get the turbulence and other issues that can cause flow to drop off."

To come close to the 440-liter/min flow rate with a more traditional pneumatic valve design, Norgren engineers say they would have needed 18-mm-wide valves, instead of the 10-mm-wide versions that they used.
Moreover, the configuration simplified assembly of the PCB routing machine because it allowed the valves to simply snap onto a standard DIN (Deutsches Insitut fur Normung eV) rail, thereby speeding manufacturing.

The high flow rate of Norgren's V10 valves, enabled engineers to employ 10-mm-wide valves, instead of 18-mm designs.

During operation of the routing machine, the VM10 valves deliver air at three different pressures: 15 psi for normal operation of the "pressure feet" that hold the PC boards in place; 60 psi for situations calling for tighter pressure-foot clamping; and 80 psi for other pneumatic functions, such as opening and closing the chuck inside the router's spindle.

By choosing pneumatics over electrics to accomplish all that, Norgren engineers claim they helped make the machine smaller and less costly. "If you do this electrically, then you're dealing with power amplifiers and linear motors or lead screws, which add up in cost," Gibbons concludes. "Pneumatics are the most economical way to go for a project like this."

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